T Cell Memory Generation and Function: Our strategy in this program is to apply the knowledge acquired in recent years to directly investigate the basic biology of immune memory. These advances include, new understandings of the mechanisms of lymphocyte recognition, antigen presentation, lymphocyte activation and programmed cell death. We will make use of new tools to approach important questions about memory T cells including; T cell receptor transgenic mice and mice deficient in lymphocyte subsets or in molecules involved in immune responses (knockout mice) and ne adoptive transfer models of lymphocyte response as well as methods to visualize T cells in situ. We have characterized CD4 and CD8 T memory cells and have developed in vitro and in vivo models in which their generation can be assessed and their in vivo migration visualized. We will determine the factors which are required for CD4 and CD8 memory T cell generation, persistence and migration. Project 1: Regulation of CD4 T Cell Memory Development and Function (Swain) will focus on the factors necessary for the generation of CD4 memory. This will be determined both by manipulating the in vitro generation of activated CD4 T cells to a pre-memory state, where transfer to adoptive hosts in the absence of antigen results in memory formation and by examining the host factors required for the transition from pre- memory to memory. The roles of antigen-stimulation, key cytokines and co-stimulatory interactions, chemokines and adhesion molecules will be determined and the mechanisms responsible for each step examined. With Project 2, we will directly compare the requirements of CD4 and CD8 cells and we will collaborate with Project 3 to examine the role of these same factors in memory CD4 T cell migration. Project 2: Regulation of CD8 T Cell Memory Generation (Dutton) will focus on the factors necessary for the generation of CD8 memory examining the roles of antigen dose and duration, co-stimulatory interactions and growth and survival cytokines for their ability to generate pre-memory cells and for the transition in vivo from pre-memory and memory cells. The possibility that there is a distinct memory precursor cell will be investigated. The nature and function of CD8 memory cells will be determined. Direct comparison of CD4 and CD8 memory generation will be done in collaboration with Project 1 and the roles of the different factors in CD8 memory T cell migration will be done as a collaboration with Project 3. Project 3: Memory T Cell Migration (Bradley), will concentrate on in vivo studies addressing the molecular interactions that regulate memory lymphocytes go and how they get there. These studies will include evaluations of efficient protocols for generating memory in immunological sites where it is needed. The studies will determine the roles of antigen, of cytokines, of adhesion molecules and of chemokines in regulating memory T cell migration following antigen stimulation. The project will collaborate with Projects 1 and 2 to determine whether CD4 and CD8 memory populations generated under different conditions have distinct pathways of migration and distinct mechanism. Together these studies will provide a comprehensive picture of some of the most important aspects of regulating the development of memory including the roles of specific antigen and the interactions of the specific lymphocytes with one another, with other regulatory cells such as antigen-presenting cells and with their milieu. By combining their expertise and exchanging their findings the investigators will be able to capitalize on each other's observations and importantly, design joint experiments which would not otherwise be feasible. We believe these studies will pinpoint aspects of memory generation that will provide the basis for rational vaccine development and for intervention in the immunization process with the potential to considerably enhance the efficacy of immunization.